ZE41:A Magnesium Alloy with Improved Mechanical Properties for Use in Helicopter Transmission Castings

The high strength to weight ratio, low density and high stiffness of some magnesium alloys, has resulted in their use in cast helicopter transmission housings for many years. Traditionally U.S. manufacturers have used one of two magnesium aluminum zinc alloys-AZ91C-T6 or AZ92A-T6. Recent U.S. Army helicopter design projects (UTTAS/AAH) have upgraded transmission performance criteria in the areas of elevated temperature mechanical property retention and ability to withstand crash loading conditions. An alternative material, ZE41A magnesium alloy, was considered for use because of its improved mechanical properties. This paper will compare mechanical properties of ZE41A and AZ91/92 alloys, including fracture toughness and ballistic tolerance data not previously published. Other advantages and disadvantages of their use will be considered. Finally, the approach of one helicopter manufacturer to meeting the UTTAS performance requirements using ZE41 alloy will be presented.